Virus-removing ultrafiltration membrane and preparation method thereof

Abstract

The invention provides a virus-removing ultrafiltration membrane and a preparation method thereof, and belongs to the technical field of membrane separation. According to the preparation method of the ultrafiltration membrane, a hydrophilic polymer and a bulk polymer are blended to prepare a membrane casting solution, the ultrafiltration membrane is prepared on the basis of a double-layer homogeneous compounding method and a phase inversion method, and the obtained integrated ultrafiltration membrane comprises a separation layer with a compact skin layer and a pre-filtration supporting layer with a complete sponge structure, and provides high mechanical strength and toughness at the same time; the separation layer and the supporting layer form a hourglass-shaped structure with effective aperture continuously changing in a gradient mode, and no obvious interface or layering phenomenon exists. The ultra-filtration membrane is clear in gradient structure, the upper surface is loose, the lower surface is compact, the structures are fused more tightly, no obvious interface exists, the filtration resistance is reduced, and the protein permeability is improved. And the flux and the maximum treatment volume are improved and the treatment time is shortened while the relatively high virus rejection rate and the relatively low protein adsorption capacity are maintained.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and particularly relates to a virus-removing ultrafiltration membrane and a preparation method thereof. Background Art

[0002] With the progress and development of technology, antibodies obtained by biological cell culture are widely used in the medical field. The production of biological products usually uses microorganisms or human / animal cells, tissues, and body fluids, etc. as raw materials or auxiliary materials. However, during cell culture and downstream purification production processes, these raw materials or auxiliary materials are extremely vulnerable to virus contamination, seriously affecting the safety of biological products. Therefore, inactivating and removing viruses in biological products is one of the indispensable important links. Currently, the main methods for virus inactivation or removal include dry heat inactivation method, pasteurization method, organic solvent / detergent (S / D) method, column chromatography method, and membrane filtration method, etc. Among them, the membrane filtration method utilizes the difference in the sizes of viruses and proteins. Mainly through the size sieving effect, protein molecules smaller than the average pore size (for example, monoclonal antibodies, whose size is about 12 nm) pass through the filter membrane, and viruses larger than the average pore size (such as parvovirus, the virus particles are round, and its diameter is 21 - 24 nm) are intercepted, thereby achieving the effect of virus removal. The membrane filtration method can not only meet the requirements of good virus removal effect, high permeability of target proteins, but also meet the characteristics of no denaturation of target proteins. In addition, whether it is an enveloped virus or a non-enveloped virus, whether the virus genome is RNA or DNA, it can be completed by the membrane filtration method.

[0003] The membrane filtration method is a precise separation technology that uses a membrane as a filtration medium and utilizes the selective permeability of membrane pores. Under the action of driving forces such as pressure difference, solvents, inorganic ions, small molecules, or proteins, etc. pass through the membrane, while viruses, particles, and macromolecules are intercepted. For organic polymer membranes, the main preparation methods include phase inversion method, stretching method, track etching method, and sintering method, etc. Among them, the phase inversion method is widely used due to its convenient operation, simple equipment, and good controllability of membrane structure, etc., which has greatly promoted the development of membrane technology. The phase inversion method can be divided into non-solvent induced phase separation (NIPS), thermally induced phase separation (TIPS), reverse thermally induced phase separation (RTIPS), and solvent evaporation phase separation method (VIPS), etc. according to different methods.

[0004] The NIPS method is the most commonly used method for preparing polymer membranes by phase inversion. First, the polymer, solvent and additives are mixed and dissolved to prepare a uniform polymer solution or a casting solution, and then the polymer solution is scraped or cast into a thin film on a support (such as a glass plate, a non-woven fabric, etc.), and then immediately immersed in a non-solvent coagulation bath to undergo phase separation and solidification to form a film. Chinese patent CN116943451B discloses a method for preparing a polyethersulfone (PES) virus removal filter membrane using the NIPS method. However, the phase inversion process of the NIPS method membrane is difficult to accurately control the membrane formation process due to its instantaneous nature, and the prepared membrane has a wide pore size distribution and mechanical strength that needs to be improved.

[0005] The TIPS method is based on temperature changes to trigger phase inversion. The TIPS method is to mix a polymer and a diluent (usually a solvent or a small molecule additive) at high temperature to form a uniform solution. When the temperature is lowered, the compatibility between the polymer and the diluent changes, resulting in phase separation into a membrane. International patent WO2018 / 088232 discloses a method for preparing polyvinylidene fluoride (PVDF) hollow fiber virus removal membrane using the TIPS method. The TIPS method can prepare membranes with high strength and good pore structure, but it is only applicable to some polymer materials with high thermal stability requirements, and it is difficult to control small pores (~20nm).

[0006] The RTIPS method is also based on temperature changes to trigger phase transformation. However, it requires the use of a low critical solution temperature (LAST) casting liquid system, that is, for certain polymer-solvent systems, at a relatively low temperature, the polymer and the solvent dissolve in each other to form a stable homogeneous system. When the temperature rises to a certain value, the solubility of the polymer in the solvent drops sharply, and phase separation occurs to form a film. U.S. Patent US10118133B2 discloses a method for preparing a PES virus removal filter membrane by the RTIPS method using a casting liquid system with LAST. The membrane prepared by the RTIPS method will form a denser membrane or a membrane with a special pore structure due to the rapid solidification of the polymer during the heating process. However, there are fewer special casting liquid systems suitable for the RTIPS method, and the membrane pore size is usually relatively large (~100nm).

[0007] Currently, membrane materials used as virus removal membranes include regenerated cellulose (CA), polysulfone (PSF), polyethersulfone (PES), and polyvinylidene fluoride (PVDF), etc. Among them, PES has good thermal stability, excellent chemical stability, high strength, good mechanical properties, and good biocompatibility, making it a preferred virus removal membrane material. However, generally, pure polymer membrane materials are affected by molecular structure and membrane preparation parameters, and have problems such as poor permeability, poor anti-protein adsorption ability, and short service life. For example, US Patent US10118133B2 discloses a stacked multi-layer composite PES ultrafiltration membrane with at least one ultrafiltration layer, which is prepared by a co-casting method. This membrane has a good retention effect on parvovirus and high flux, and can effectively meet the actual needs. However, in the stacked multi-layer composite method, if there is an intermolecular repulsive force between the two casting solutions, two-phase or multi-phase interfaces will inevitably be generated during the composite process, increasing the filtration resistance. At the same time, this patent selects PES with strong hydrophobicity as the polymer, and the poor hydrophilicity will lead to serious protein adsorption, resulting in low membrane flux and protein recovery rate. To improve the permeation separation performance and anti-pollution or anti-protein adsorption performance of virus removal filter membranes, appropriate hydrophilic modification of the filter membranes is required.

[0008] Common hydrophilic modifications of ultrafiltration membranes include bulk modification, surface modification, and blending modification, etc. Among them, bulk modification is to introduce hydrophilic monomers during the polymerization reaction to copolymerize or graft with the bulk polymer or monomers to prepare hydrophilic polymers, so that the obtained filter membranes have hydrophilicity. For example, Chinese Invention Patent CN118594294A discloses a polysulfone-based block copolymer porous membrane for efficient separation of viruses and antibodies. Among them, the polysulfone-based block copolymer is a block copolymer formed by chemically bonding a hydrophilic block A and a polysulfone-based high polymer block B. The hydrophilic block A is one or more of high molecular materials such as polyethylene glycol and monomethyl ether of polyethylene glycol, and the polysulfone high polymer block B is one or more of polysulfone-based materials such as polysulfone and polyethersulfone. The polysulfone-based block copolymer porous membrane has a retention rate of more than 4 log for parvovirus with a size of more than 15 nm, and a recovery rate of more than 98% for antibodies, and has excellent virus and antibody separation performance. However, the bulk modification synthesis process is complex, the cost is high, the mechanical strength of the formed membrane is usually low, and there are risks such as polymer stability.

[0009] Surface modification can be further divided into surface coating modification and surface crosslinking modification. Surface coating modification is to coat hydrophilic materials on the surface of the polymer membrane to form a hydrophilic layer through hydrogen bonding, van der Waals forces, etc., so as to improve the hydrophilicity of the membrane surface. For example, US Patent US4413074A discloses a hydrophobic polymer (PES) membrane matrix, the surface of which is coated with hydroxyalkyl cellulose and treated with water vapor to form a hydrophilic surface, and can have a pure water flux greater than (~1500L / m 2)。However, hydroxyalkyl cellulose is difficult to penetrate into the small pores of the ultrafiltration membrane, and its hydrophilic effect or anti-protein adsorption property is slightly insufficient; moreover, the surface coating modification effect will gradually fall off as the storage time prolongs, resulting in weakened hydrophilicity, and the stability needs to be improved.

[0010] In addition, surface cross-linking modification uses chemical treatment methods to directly introduce hydrophilic groups onto the membrane surface to improve the hydrophilicity of the membrane. For example, Chinese invention patent CN114653222B discloses a virus-removing filter membrane with low protein adsorption and its preparation method. The filter membrane is a PES filter membrane or a PVDF filter membrane, including a pre-filtration area, a separation area for intercepting viruses, and a hydrophilic cross-linked layer. The hydrophilic cross-linked layer is formed by ultraviolet irradiation cross-linking of hydrophilic monomers and cross-linking agents, covering the surface of the fiber solid part of the separation area, greatly reducing the protein adsorption of the filter membrane. During use, the flux changes slowly, the loading capacity is large, and the protein recovery rate is high. However, the process technology of surface cross-linking modification is more complex, and the types of surface modification available are less, and the actual effect and stability still need to be improved.

[0011] Blending modification is to add inorganic, organic or amphiphilic modification particles to the polymer system and blend them with the polymer matrix efficiently to improve the hydrophilicity of the filter membrane. Among them, directly blending and adding hydrophilic membrane materials is a relatively preferred method. In recent years, hydrophilic polymer materials such as sulfonated polyethersulfone (SPES) and hydroxyl-terminated polyethersulfone (PES-OH) have been widely used in the preparation of macroporous microfiltration membranes with excellent performance. The reason is that the hydrophilic polymer has the same or similar repeating unit structure as the polymer matrix, good compatibility, and is easy to form a homogeneous polymer solution under a certain blending ratio condition. For example, Chinese patent CN117563441A discloses a low-protein adsorption PES sterilization membrane and its preparation method. This method realizes the hydrophilization of the PES microfiltration membrane by adding sulfonated polyethersulfone (SPES) to the casting solution system. The average pore diameter of the sterilization membrane is 0.15 - 0.4 μm, and at the same time, the obtained microfiltration membrane has a significantly reduced protein adsorption rate, high retention efficiency, and high flux. By directly using membrane materials with hydrophilic groups, the operation is simple and permanent hydrophilic modification can be achieved, but the strength of the polymer membrane is relatively low and it is difficult to prepare small-pore membranes (~20 nm). In addition, introducing a mesoporous layer or an intermediate layer in Chinese patent CN117504628A will inevitably increase the filtration resistance and the difficulty of forming and processing.

[0012] In addition, during the current virus removal membrane filtration process, due to the high protein concentration in the feed liquid (20 - 23 g / L) and relatively high operating pressure (50 psi or 0.3 - 0.4 MPa), high requirements are imposed on the mechanical properties and hydrophilicity of the filter membrane. The excellent tensile strength and elongation at break (toughness) of the filter membrane can maintain good integrity and stability during the processing and use of the membrane filter. However, currently commercial filter membranes all have the problem of low toughness. For example, CN114653222B discloses a virus removal filter membrane with low protein adsorption and its preparation method. The elongation at break of the virus removal filter membrane prepared by this method is all < 10%, and there is a risk of rupture during actual use.

[0013] And Chinese CN114345151 B discloses a polymer ultrafiltration membrane with high toughness and high anti-pollution performance and its preparation method. It dissolves any one of polyvinylidene fluoride, polyvinyl chloride, and polyacrylonitrile and polystyrene-maleic anhydride in an appropriate amount of organic solvent to form a homogeneous solution, uses polyethylene glycol as an additive and modifier, regulates the structure of the polymer / polystyrene-maleic anhydride blend ultrafiltration membrane through the reaction-induced phase separation method, and controls the grafting rate of the reaction. And directly uses the reaction system at this moment as the casting solution, and prepares the polymer / polystyrene-maleic anhydride grafted polyethylene glycol ultrafiltration membrane by the immersion precipitation phase separation method. Due to the intermolecular and intramolecular forces between the matrix polymer and the hydrophilic polymer, the ultrafiltration membrane prepared based on this has significantly improved toughness and anti-pollution properties while ensuring high flux and high retention. However, the average pore size of the ultrafiltration membrane prepared by this method is too small (6 - 8 nm), and the protein retention is too large, so it cannot be used in the field of virus removal filtration.

[0014] Generally speaking, the problems existing in the current nano-scale virus removal filter membranes are insufficient hydrophilicity, resulting in relatively high protein adsorption, low protein flux, insufficient toughness of the filter membrane, and excessive filtration resistance, and there are stability risks during the processing and actual use of the membrane filter. The existence of these problems also restricts the development of virus removal filter membranes to a certain extent. Summary of the Invention

[0015] The present invention provides a virus removal ultrafiltration membrane and its preparation method. The ultrafiltration membrane is prepared by blending a hydrophilic polymer and a matrix polymer to prepare a casting solution based on the double-layer homogeneous composite method and the phase separation method, and by means of the intermolecular and intramolecular forces between the matrix polymer and the hydrophilic polymer, the blending compatibility of the casting solution and the mechanical properties of the composite membrane can be significantly improved, and finally a high-toughness virus removal ultrafiltration membrane with high virus retention rate, high protein loading capacity, and high feed liquid filtration flux is obtained.

[0016] To achieve the above object, the present invention provides a method for preparing a virus-removing ultrafiltration membrane, which is prepared by blending a hydrophilic polymer and a matrix polymer to prepare a casting solution based on a double-layer homogeneous composite method and a phase inversion method. The obtained integrated ultrafiltration membrane includes a separation layer with a dense skin layer and a pre-filter support layer with a complete sponge structure. The separation layer and the support layer form a sand funnel-shaped structure with a continuously varying effective pore size gradient and no obvious interface or delamination phenomenon.

[0017] Preferably, the preparation based on the double-layer homogeneous composite method and the phase inversion method is specifically as follows:

[0018] Blend the matrix polymer, hydrophilic polymer, solvent and additive to prepare two casting solutions A and B with the same or similar composition and different viscosity ranges.

[0019] Combine the obtained casting solutions A and B on a carrier by a co-casting method, and casting solution A covers casting solution B to obtain a nascent membrane.

[0020] Immerse the carrier and the nascent membrane together in a coagulation bath at a certain temperature for phase inversion, then immerse them in hot water at 40 - 60 °C for sufficient water washing, and then dry them at 75 - 85 °C to obtain the virus-removing ultrafiltration membrane.

[0021] Preferably, by mass percentage, the addition amounts of each component in casting solution A are: matrix polymer: 18% - 24%, hydrophilic polymer: 2% - 5%, solvent: 40% - 50%, additive: 28% - 35%; the addition amounts of each component in casting solution B are: matrix polymer: 14% - 16%, hydrophilic polymer: 2% - 6%, solvent: 24% - 30%, additive: 52% - 58%.

[0022] Preferably, at 25 °C, the viscosity range of casting solution A is 20000 mPa·s - 25000 mPa·s, and the viscosity range of casting solution B is 10000 mPa·s - 15000 mPa·s.

[0023] Preferably, the matrix polymer is selected from at least one of polyethersulfone (PES), polysulfone (PSF), polyvinylidene fluoride (PVDF), and polyvinyl chloride (PVC); the hydrophilic polymer is selected from at least one of sulfonated polysulfone (SPSF), hydroxyl-terminated polyethersulfone (PES-OH), sulfonated polyethersulfone (SPES), and polyethersulfone-polyethylene glycol block copolymer (PES-b-PEG).

[0024] It is understandable that when PES-OH (or PES-b-PEG) is solely selected as the hydrophilic modification material, adding a relatively high mass ratio of PES-OH (PES-b-PEG) in the system or formulating the casting solution with pure PES-OH (PES-b-PEG) (PES-OH:PES blend mass ratio > 50:50 wt. / wt.) can introduce more hydrophilic groups. However, due to the relatively low molecular weight of PES-OH, the viscosity of its casting solution is low, the film-forming effect is poor, and the strength of the film is very low. When a relatively small mass ratio of PES-OH (or PES-b-PEG) (PES-OH:PES blend ratio < 10:90 wt. / wt.) is added to the system for blending hydrophilic modification, the hydrophilic modification effect is poor due to the small number of grafted hydrophilic groups in PES-OH or PES-b-PEG. Therefore, the preferred addition amount of PES-OH or PES-b-PEG includes but is not limited to 10 - 30 wt.%.

[0025] When solely selecting SPES (sulfonation degree: 10 - 20%) as the hydrophilic modification material, through theoretical calculation, SPES (sulfonation degree: 10 - 20%) and PES are a partially compatible system, and the introduction of sulfonic acid groups will reduce the strength of the ultrafiltration membrane. Therefore, adding too much SPES will cause the strength of the filter membrane to deteriorate. Therefore, the preferred addition amount of SPES includes but is not limited to 0 - 30 wt.%.

[0026] Preferably, the solvent of the casting solution is selected from at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), γ-valerolactone (GVL); the additives of the casting solution are selected from at least one of triethylene glycol (TEG), diethylene glycol (DEG), isopropyl alcohol (IPA), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG).

[0027] Preferably, the coagulation bath includes at least one of water, ethanol, DMF, NMP, and DMAc, and the temperature of the coagulation bath is 30 - 60°C.

[0028] Preferably, the coating carrier is selected from at least one of polyethylene (PE), polypropylene (PP), polyester (PET), and polycarbonate (PC).

[0029] Preferably, the phase inversion method is selected from at least one of NIPS, TIPS, and RTIPS.

[0030] Preferably, the co-casting method is selected from one of the double-layer synchronous scraping process, double-layer slit spraying process, and scraping - spraying process.

[0031] It is understandable that the common co-casting process for preparing double-layer or multi-layer composite membranes includes, but is not limited to, layer-by-layer coating, double-layer synchronous knife coating process, double-layer slot spraying process, and knife coating-spraying process, etc. Among them, the double-layer knife coating process: has high requirements for equipment accuracy, and is prone to obvious interfaces or even delamination phenomena, and at the same time has poor uniformity (unable to ensure the uniformity of the two layers separately); the double-layer slot spraying process has a high manufacturing cost, and spraying is more suitable for systems with a relatively thin coating thickness; the knife coating-spraying process: the uniformity of the slot spraying process is higher than that of the knife coating. The support layer is selected by the knife coating process and then the dense layer is sprayed on. The two layers do not affect each other, which can ensure uniformity while saving costs.

[0032] The two prepared casting solutions are synchronously and uniformly cast on a flat, smooth and moving carrier through a synchronous composite coating device at a certain speed, and then immersed in a coagulation bath. At this time, a solvent-nonsolvent double diffusion occurs between the casting solution and the coagulation bath. The solvent in the casting solution diffuses into the coagulation bath, while the nonsolvent in the coagulation bath diffuses into the casting solution. After a period of time, the double diffusion reaches equilibrium, and the casting solution becomes thermodynamically unstable, resulting in delamination and finally forming an asymmetric structure membrane.

[0033] Preferably, the running speed is 3-15 m / min; it is also understandable that by adjusting the running speed of the equipment, the exchange rate of the solvent and the nonsolvent in the coagulation bath will be affected. When the running speed increases, the mass transfer process between the coagulation bath and the casting solution speeds up, which is beneficial to the phase inversion membrane formation and pore structure regulation of the ultrafiltration membrane. And increasing the running speed has a stretching effect on the membrane sheet, so an ultrafiltration membrane with a more uniform pore size distribution can be obtained.

[0034] The present invention also provides a high-toughness and high-flux virus-removing ultrafiltration membrane obtained by the preparation method according to any one of the above. The obtained integrated ultrafiltration membrane includes a separation layer with a dense skin layer and a pre-filter support layer with a complete sponge structure, which provides high mechanical strength and toughness at the same time; the separation layer and the support layer form an hourglass-shaped structure with a continuously changing effective pore size gradient, and there is no obvious interface or delamination phenomenon.

[0035] Preferably, the pure water permeability of the obtained ultrafiltration membrane is 600-900 L m -2 h -1 bar -1 , the protein recovery rate > 99%, the virus interception rate is not less than LRV6, and the thickness of the ultrafiltration membrane is 120-170 μm.

[0036] Preferably, the tensile strength of the ultrafiltration membrane is 6.0-9.0 MPa, and the elongation at break is 30-50%.

[0037] Preferably, the PMI average pore size of the ultrafiltration membrane is 16 - 22 nm, the SEM particle size range is 16 - 37 nm, and the upper surface porosity is 15 - 35%; the SEM particle size range of the lower surface of the support layer is 0.32 - 1.48 μm, and the lower surface porosity is 25 - 45%; the ratio of the pore sizes of the upper and lower surfaces is 1:6 - 1:90, and a more suitable ratio is 1:19 - 1:31.

[0038] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0039] 1. In terms of the blending hydrophilic modification method: The method of blending and modifying with a bulk polymer and a hydrophilic polymer containing sulfonic acid or hydroxyl groups, etc., significantly improves the toughness of the ultrafiltration membrane and enhances the compressive performance by means of the intermolecular and intramolecular forces (such as hydrogen bonds) between the bulk polymer and the hydrophilic polymer.

[0040] 2. Homogeneous composite method: Two casting solutions with the same polymer type, composition, and properties (different solid contents) are used in a co-casting method (such as one of the double-layer slit spraying process and the scraping-spraying process), that is, homogeneous composite. The prepared integrated ultrafiltration membrane includes a separation layer with a dense skin layer and a pre-filter support layer with a complete sponge structure, which simultaneously provides high mechanical strength and toughness. The separation layer and the support layer form an hourglass-shaped structure with a continuous gradient change in the effective pore size, and there is no obvious interface or delamination phenomenon; the fusion between the multi-layer structures is closer, which is beneficial to reducing the filtration resistance and improving the protein permeability. While maintaining a high virus retention rate and a lower protein adsorption amount, the flux and the maximum treatment volume are increased, and the treatment time is shortened.

[0041] 3. In terms of the preparation mechanism of the ultrafiltration membrane: For the prepared integrated ultrafiltration membrane, due to the difference in viscosity, under the same process conditions, the upper high-viscosity casting solution phase-transforms into a dense separation layer with a smaller PMI average pore size (16 - 22 nm), which plays a role in intercepting viruses; the lower low-viscosity casting solution phase-transforms into a pre-filter support layer with a larger average pore size (0.32 - 1.48 μm), which has a lower filtration resistance and higher mechanical strength.

[0042] 4. In terms of hydrophilicity and protein adsorption: The introduction of hydrophilic groups in the ultrafiltration membrane can effectively improve the hydrophilic performance of the ultrafiltration membrane. The improvement of the hydrophilic performance will increase the permeation flux while reducing protein adsorption, and correspondingly, the protein recovery rate will also increase.

[0043] 5. In terms of virus retention mechanism: The sieving mechanism of the ultrafiltration membrane is the size effect and the electrostatic repulsion effect. Since the addition of a hydrophilic polymer with a charge or a negatively charged group (such as sulfonated polyethersulfone) to the ultrafiltration membrane casting solution can increase the charge of the ultrafiltration membrane. Common protein antibodies are all negatively charged substances, and an electrostatic repulsion occurs between the sulfonic acid group and the protein antibody. That is to say, the combined effect of the size effect and the electrostatic repulsion of the ultrafiltration membrane can further improve the virus retention rate, reduce the protein adsorption amount, and at the same time increase the flux and the maximum feed liquid treatment volume, and shorten the treatment time. Description of the Drawings

[0044] Figure 1 It is a schematic SEM diagram of the cross-section of the ultrafiltration membrane obtained in Example 1, with a magnification of 400×;

[0045] Figure 2 It is a schematic SEM diagram of the upper surface of the ultrafiltration membrane obtained in Example 1, with a magnification of 5,000×;

[0046] Figure 3 It is a schematic SEM diagram of the lower surface of the ultrafiltration membrane obtained in Example 1, with a magnification of 50k×;

[0047] Figure 4 It is a comparison chart of the mechanical properties of the ultrafiltration membranes obtained in Examples 1-4;

[0048] Figure 5 It is a comparison chart of the mechanical properties of the ultrafiltration membranes obtained in Comparative Examples 1-3. Detailed Embodiments

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] Test methods for the performance and physical parameters of the following embodiments and comparative examples

[0051] 1. Pure water permeability: The virus removal composite membrane prepared by the present invention is clamped in a membrane cell with an effective area of 7.065 cm 2 . It is pre-pressed for 30 minutes at an operating pressure of 1.5 bar to make the pure water permeability stable, and then the pressure is adjusted to 1 bar for testing. The pure water permeability can be obtained by the following formula:

[0052]

[0053] Among them, PWP is the pure water permeability (LMH bar -1 ), V is the volume of the filtrate (L), and A is the effective test area of the membrane (m2 ), where t is the test time (h).

[0054] 2. Mechanical properties: The virus-removing composite film prepared by the present invention was made into a spline of 5×50 mm, and the breaking strength and elongation at break of the film were tested using a precision tensile tester at a tensile speed of 5 mm / min.

[0055] 3. Average pore size test: The PMI pore size and pore size distribution of the virus-removing composite film prepared by the present invention were tested using a gas-liquid interface pore size analyzer of the Porometer 1000L model.

[0056] 4. Virus retention challenge: Polyclonal antibody IgG was used as the antibody solution, and then a certain amount of MS2 phage (Ames virus) was added to the prepared antibody solution and stirred well to obtain an antibody solution containing the virus. A dead-end filtration device was used for the virus retention challenge test. The virus removal rate can be calculated by the following formula:

[0057]

[0058] Among them, LRV represents the logarithmic removal rate of the virus, C0 is the infection titer of the stock solution containing the virus antibody, and C p represents the infection titer in the filtrate.

[0059] 5. Protein recovery rate: An IgG solution with a concentration of 10 g / L was prepared and pre-filtered to remove particles and protein aggregates. Then, the dead-end filtration device was also used for the test. The concentration of the protein was measured by its absorbance at 280 nm using an ultraviolet spectrophotometer (SHIMADZU, UV-2600). The recovery rate can be obtained by the following formula:

[0060]

[0061] Among them, R is the protein recovery rate, C p is the concentration of IgG in the filtrate, and C0 is the concentration of IgG in the stock solution.

[0062] 6. Thickness test: 10 points were randomly sampled on the film using a micrometer thickness gauge and the average value was calculated.

[0063] Example 1

[0064] The ultrafiltration membrane of Example 1 was prepared by co-casting of scraping-spraying. First, the hydrophilic polymers (SPES and PES-OH) were blended with the matrix polymer (PES) in a certain proportion to prepare two homogeneous polymer solutions with different concentrations, and then the co-casting equipment was used to cast them on the support carrier, and the ultrafiltration membrane was prepared by the phase inversion method. The advantage of Example 1 is that the introduction of hydrophilic polymers can improve the hydrophilicity of the ultrafiltration membrane and the strength of the ultrafiltration membrane. The following is a more specific description of Example 1:

[0065] Taking the polymer PES (average molecular weight 50000 Da) as the matrix polymer, SPES and PES-OH as the hydrophilic polymers, NMP as the solvent, and DEG as the additive, two casting solutions a and b were prepared;

[0066] Preparation of casting solution a: PES, SPES (sulfonation degree: 20%), additive DEG, solvent NMP, etc. were prepared into casting solution a according to the mass ratio of 18:4:28:50. Stir at 70 °C to completely dissolve the polymer into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution was measured to be 23800 mPa s (25 °C).

[0067] Preparation of casting solution b: PES, PES-OH (terminal hydroxyl content ≥ 50%), additive DEG, solvent NMP, etc. were prepared into casting solution b according to the mass ratio of 15:3:58:24. Stir at room temperature to completely dissolve the polymer into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution was measured to be 12400 mPa s (25 °C).

[0068] The obtained casting solutions a and b were combined on the PET carrier membrane by co-casting of scraping-spraying, and casting solution a covered casting solution b to obtain the nascent membrane; then the carrier membrane and the nascent membrane were immersed in a coagulation bath at 50 °C for phase inversion, and then immersed in hot water at 50 °C for sufficient water washing to remove the residual solvent in the membrane, and then dried at 85 °C to obtain the virus-removing ultrafiltration membrane. The SEM schematic diagrams of the cross-section, upper surface and lower surface of the obtained high-toughness and high-flux virus-removing ultrafiltration membrane are respectively as Figures 1-3 shown.

[0069] The average pore size of the ultrafiltration membrane was measured to be 21.3 nm, the pure water permeability was 900 L m -2 h -1 bar -1 , the tensile strength was 8.3 MPa, and the elongation at break was 48% (see Table 1 and Figure 4 ).

[0070] Example 2

[0071] Example 2 is basically the same as Example 1, except that the raw materials for film formation are the matrix polymer (PSF) and the hydrophilic polymer (SPSF). The following is a more specific description of Example 1:

[0072] Prepare casting solution a: PSF, SPSF (sulfonation degree: 20%), additive DEG, solvent NMP, etc. are prepared into casting solution a according to a mass ratio of 18:4:28:50. Stir at 70 °C until the polymer is completely dissolved into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution is measured to be 24500 mPa·s (25 °C).

[0073] Prepare casting solution b: PSF, SPSF (sulfonation degree: 20%), additive DEG, solvent NMP, etc. are prepared into casting solution b according to a mass ratio of 15:3:58:24. Stir at room temperature until the polymer is completely dissolved into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution is measured to be 11000 mPa·s (25 °C).

[0074] The specific implementation method of Example 2 refers to Example 1. The average pore size of the ultrafiltration membrane is measured to be 20.5 nm, and the pure water permeability is 780 L m -2 h -1 bar -1 , the tensile strength is 7.9 MPa, and the elongation at break is 35% (see Table 1 / Figure 4 ).

[0075] Example 3

[0076] Example 3 is basically the same as Example 1, except that the raw materials for film formation are PES, SPES, PES-b-PEG, and the additive is polyethylene glycol (PEG-400). The following is a more specific description of Example 3:

[0077] Prepare casting solution a: PES, SPES, additive polyethylene glycol (PEG-400), solvent NMP, etc. are prepared into casting solution a according to a mass ratio of 18:5:35:42. Stir at 70 °C until the polymer is completely dissolved into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution is measured to be 21200 mPa·s (25 °C).

[0078] Prepare casting solution b: PES, PES-b-PEG, additive polyethylene glycol (PEG-400), solvent NMP, etc. are prepared into casting solution b according to a mass ratio of 16:2:58:24. Stir at room temperature until the polymer is completely dissolved into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution is measured to be 11800 mPa·s (25 °C).

[0079] The specific implementation method of Example 3 refers to Example 1. The average pore size of the ultrafiltration membrane is measured to be 22 nm, and the pure water permeability is 840 L m -2 h-1 bar -1 with a tensile strength of 7.8 MPa and an elongation at break of 42% (see Table 1 / Figure 4 ).

[0080] Example 4

[0081] Example 4 is basically the same as Example 3, except that the raw materials for film formation are hydrophilic polymer (PES-b-PEG) and matrix polymer (PES). The following is a more specific description of Example 4:

[0082] Prepare casting solution a: PES, PES-b-PEG, additive polyethylene glycol (PEG-400), solvent NMP, etc. are prepared into casting solution a according to a mass ratio of 18:5:35:42. Stir at 70 °C to completely dissolve the polymer into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution is measured to be 23300 mPa·s (25 °C).

[0083] Prepare casting solution b: PES, PES-b-PEG, additive polyethylene glycol (PEG-400), solvent NMP, etc. are prepared into casting solution b according to a mass ratio of 16:2:58:24. Stir at room temperature to completely dissolve the polymer into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution is measured to be 12000 mPa·s (25 °C).

[0084] The specific implementation method of Example 4 refers to Example 1. The average pore size of the ultrafiltration membrane is measured to be 21.5 nm, and the pure water permeability is 720 L·m -2 h -1 bar -1 with a tensile strength of 7.2 MPa and an elongation at break of 36% (see Table 1 / Figure 4 ).

[0085] Comparative Example 1

[0086] The key point of Comparative Example 1 is that the ultrafiltration membrane is prepared by scrape-spray co-casting. The difference is that two casting solutions a and b are prepared with polymer PES (average molecular weight 65000 Da) as the matrix polymer, TEG as the additive, NMP as the solvent, etc.:

[0087] Prepare casting solution a: PES, additive triethylene glycol (TEG), solvent NMP, etc. are prepared into casting solution a according to a mass ratio of 24:36:40. Stir at 70 °C to completely dissolve the polymer into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution is measured to be 22600 mPa·s (25 °C).

[0088] Preparation of casting solution b: PES, additive triethylene glycol (TEG), solvent NMP, etc. were used to prepare casting solution b according to a mass ratio of 20:56:24. Stir at room temperature until the polymer is completely dissolved into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution was measured to be 10800 mPa s (25 °C).

[0089] The specific implementation method of Comparative Example 1 refers to Example 1. The average pore size of the ultrafiltration membrane was measured to be 20.3 nm, and the pure water permeability was 330 L m -2 h -1 bar -1 , the tensile strength was 5.3 MPa, and the elongation at break was 20% (see Table 1 / Figure 5 ).

[0090] Comparative Example 2

[0091] The key point of Comparative Example 2 is that the ultrafiltration membrane is prepared by co-casting of scraping - spraying. The difference is that PES-OH (terminal hydroxyl group ≥ 50%) is used as the matrix polymer, PEG is used as the additive, and NMP is used as the solvent to prepare two casting solutions a and b:

[0092] Preparation of casting solution a: PES-OH, additive polyethylene glycol (PEG-200), solvent NMP, etc. were used to prepare casting solution a according to a mass ratio of 24:36:40. Stir at 70 °C until the polymer is completely dissolved into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution was measured to be 19600 mPa s (25 °C).

[0093] Preparation of casting solution b: PES-OH, additive polyethylene glycol (PEG-200), solvent NMP, etc. were used to prepare casting solution b according to a mass ratio of 20:56:24. Stir at room temperature until the polymer is completely dissolved into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution was measured to be 8900 mPa s (25 °C).

[0094] The specific implementation method of Comparative Example 2 refers to Example 1. The average pore size of the ultrafiltration membrane was measured to be 22 nm, and the pure water permeability was 450 L m -2 h -1 bar -1 , the tensile strength was 4.9 MPa, and the elongation at break was 18% (see Table 1 / Figure 5 ).

[0095] Comparative Example 3

[0096] The key point of Comparative Example 3 is that the ultrafiltration membrane selects PES as the matrix polymer and SPES as the hydrophilic polymer, and the additive is polyethylene glycol (PEG-200). The difference is that the ultrafiltration membrane is prepared by single-layer coating. The following is a more specific description of Comparative Example 3:

[0097] Using polymer PES (average molecular weight 65000 Da) as the matrix polymer, SPES (sulfonation degree: 20%) as the hydrophilic polymer, PEG-200 as the additive, and NMP as the solvent, a casting solution was prepared according to a mass ratio of 24:36:40. Stir at 70 °C until the polymer is completely dissolved into a transparent, clear and viscous solution. Finally, the viscosity of the casting solution was measured to be 21600 mPa s (25 °C).

[0098] The obtained casting solution was sprayed onto a PET carrier membrane through a slit device to obtain a nascent membrane; the carrier membrane and the nascent membrane were immersed in a coagulation bath at 50 °C for phase inversion, and then immersed in hot water at 60 °C for sufficient washing to remove the residual solvent in the membrane, and then dried at 80 °C to obtain a virus-removing ultrafiltration membrane.

[0099] The average pore size of the ultrafiltration membrane was measured to be 18.5 nm, and the pure water permeability was 220 L m -2 h -1 bar -1 , the tensile strength was 5.2 MPa, and the elongation at break was 21% (see Table 1 / Figure 5 ).

[0100] Comparative Example 4

[0101] Patent CN 116943451 B describes a virus-removing composite membrane and its preparation method, and its membrane properties and physical parameters are shown in Table 1.

[0102] Comparative Example 5

[0103] Patent CN101690870B describes an ultrafiltration membrane, its preparation method and application, and its membrane properties and physical parameters are shown in Table 1.

[0104] Comparative Example 6

[0105] Patent CN 114653222 B describes a technical solution in the field of membrane materials technology. Its membrane properties and physical parameters are shown in Table 1.

[0106] The membrane properties and physical parameters of Examples 1-4 and Comparative Examples 1-6 are shown in Table 1.

[0107] Table 1 Membrane properties and physical parameters of Examples 1-4 and Comparative Examples 1-6

[0108]

[0109]

[0110] As can be seen from the data in Table 1, the ultrafiltration membranes prepared by adding hydrophilic polymers to the casting solution system and using the co-casting method in Examples 1-4 all exhibited excellent separation performance. Among them, in Examples 2 and 4, since only one hydrophilic polymer was added to their systems, the hydrophilicity of the prepared ultrafiltration membranes, that is, the pure water permeability, decreased compared with that in Example 1. In addition, due to the reduction of hydrophilic groups inside the system, the tensile strength of the ultrafiltration membranes also decreased slightly, but their performance was still far better than that of the comparative examples.

[0111] By comparing Comparative Example 1 with Example 1, it can be found that the addition of hydrophilic polymers greatly improves the pure water permeability, mechanical properties and hydrophilicity (protein recovery rate) of the ultrafiltration membranes; by comparing Comparative Example 2 with Example 1, it can be found that the virus retention performance of the ultrafiltration membranes prepared by simply using hydrophilic polymers as raw materials decreased; by comparing Comparative Example 3 with Example 1, it can be found that the transmembrane resistance of the ultrafiltration membranes prepared by co-casting decreased significantly, and they could simultaneously have a high retention rate and a high permeability.

[0112] By comparing Comparative Example 4 with Example 1, it can be found that the ultrafiltration membrane prepared in Comparative Example 4 had a high protein recovery rate, but its pure water permeability and virus retention rate were much lower than those in Example 1; by comparing Comparative Example 5 with Example 1, it can be found that the pure water permeability and virus retention rate of the ultrafiltration membrane prepared in Comparative Example 5 were also much lower than those in Example 1; by comparing Comparative Example 6 with Example 1, it can be found that the ultrafiltration membrane prepared in Comparative Example 6 had a high tensile strength, but its pure water permeability and elongation at break were much lower than those in Example 1.

Claims

1. A preparation method of a virus-removing ultrafiltration membrane, characterized in that It is prepared by blending a hydrophilic polymer with a matrix polymer to prepare a casting solution, and is based on a double-layer homogeneous composite method and a phase inversion method. The obtained integrated ultrafiltration membrane includes a separation layer with a dense skin layer and a pre-filter support layer with a complete sponge structure. The separation layer and the support layer form a sand funnel-shaped structure with a continuously varying effective pore size gradient, and there is no obvious interface or delamination phenomenon.

2. The preparation method according to claim 1, wherein The preparation based on the double-layer homogeneous composite method and the phase inversion method is specifically as follows: Blend the matrix polymer with the hydrophilic polymer, solvent and additive to prepare two casting solutions A and B with the same or similar composition and different viscosity ranges. Combine the obtained casting solutions A and B on a carrier by a co-casting method, and casting solution A covers casting solution B to obtain a nascent membrane. Immerse the carrier and the nascent membrane together in a coagulation bath at a certain temperature for phase inversion, then immerse them in hot water at 40-60 °C for sufficient water washing, and then dry at 75-85 °C to obtain a virus-removing ultrafiltration membrane.

3. The preparation method according to claim 2, characterized in that, By mass percentage, the addition amounts of each component in casting solution A are: matrix polymer: 18% - 24%, hydrophilic polymer: 2% - 5%, solvent: 40% - 50%, additive: 28% - 35%; the addition amounts of each component in casting solution B are: matrix polymer: 14% - 16%, hydrophilic polymer: 2% - 6%, solvent: 24% - 30%, additive: 52% - 58%.

4. The preparation method according to claim 2 or 3, characterized in that, At 25 °C, the viscosity range of casting solution A is 20000 mPa·s to 25000 mPa·s, and the viscosity range of casting solution B is 10000 mPa·s to 15000 mPa·s.

5. The preparation method according to claim 2, characterized in that, The matrix polymer is selected from at least one of polyethersulfone, polysulfone, polyvinylidene fluoride, and polyvinyl chloride; the hydrophilic polymer is selected from at least one of sulfonated polysulfone, hydroxyl-terminated polyethersulfone, sulfonated polyethersulfone, and polyethersulfone-polyethylene glycol block copolymer.

6. The preparation method according to claim 2, characterized in that, The solvent of the casting solution is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, and γ-valerolactone; the additive of the casting solution is selected from at least one of triethylene glycol, diethylene glycol, isopropanol, polyvinylpyrrolidone, and polyethylene glycol.

7. The preparation method according to claim 2, characterized in that The coagulation bath includes at least one of water, ethanol, DMF, DMAc, and NMP, and the temperature of the coagulation bath is 30-60 °C; The phase inversion method is selected from at least one of NIPS, TIPS, and RTIPS; The co-casting method is selected from one of a double-layer synchronous scraping process, a double-layer slit spraying process, and a scraping-spraying process.

8. The virus-removed ultrafiltration membrane obtained by the preparation method according to any one of claims 1-7, characterized in that, The obtained integrated ultrafiltration membrane includes an upper separation layer with a dense skin layer and a lower pre-filter support layer with a complete sponge structure. The upper separation layer and the lower support layer are in the shape of an hourglass with a continuously varying effective pore size gradient, and there is no obvious interface or delamination phenomenon.

9. The virus-removing ultrafiltration membrane according to claim 8, characterized in that, The pure water permeability of the obtained ultrafiltration membrane is 600-900 L m -2 h -1 bar -1 , the protein recovery rate > 99%, the virus retention rate is not less than LRV6, and the thickness of the ultrafiltration membrane is 120-170 μm.

10. The virus-removing ultrafiltration membrane according to claim 8, characterized in that, The tensile strength of the ultrafiltration membrane is 6.0-9.0 MPa, and the elongation at break is 30-50%.

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